Proving the Reflection Property of an Ellipse (VIDEO!)

The Mormon Tabernacle in Salt Lake City and the Whispering Gallery in the US Capitol Building are each the shape of an ellipse. This means that if you stood at one focus of the ellipse, each sound wave from a whisper you make will bounce off the wall and head directly to the second focus point. Moreover, all the sound waves will travel the same distance and so arrive in synchronicity at that point. This means a friend standing there will hear and understand your whisper perfectly!

In this video we explain how reflections work and prove mathematically that ellipses do indeed have this astounding property.

Reflection Property of an Ellipse


    QUADRATICS, Permutations and Combinations, EXPLODING DOTS, and more!

    Written for educators - and their students too! - this website, slowly growing, takes all the content Tanton has developed in his books, videos, and workshops, and organizes it into short, self-contained, and complete, curriculum units proving that mathematics, at all points of the school curriculum, can be joyous, fresh, innovative, rich, deep-thinking, and devoid of any rote doing! Let's teach generations of students to be self-reliant thinkers, willing to flail and to use their common sense to "nut their way" through challenges, to assess and judge results, and to adjust actions to find success. (Great life skills!)


  • Books

  • Get in touch